AU741404B2 - Container - Google Patents

Description

P:\OPER\JPN2161301 spodoA-8/10101 -1-

CONTAINER

The present invention relates to a container made of plastics for bulk transportation and for use in safekeeping and transporting chemical goods, plastics, grains, fertilizers and the like. More particularly, but not exclusively, the present invention relates to an improved container having a specific ventilator-mounted design.

Bulk transportation of chemical goods, plastics, grains, fertilizers and the like is practiced on a large scale now as a part of streamlining physical distribution ways and means, and a large plastic container is used for one of the transportation means. For example, a sack in the form of a rectangular parallelepiped of 6 to 12 m in length made of a cylindrical plastic film prepared by blown-film extrusion is actually used for transporting products stored therein.

Figure 1 shows a perspective view of a container which is an example of this form.

The container 1 is as a whole made of a sack body in the form of a rectangular parallelepiped prepared by cutting a cylindrical inflation film into the required length, folding both longitudinal ends of the film and bonding the superposed portion of both ends.

This large container 1 is used for bulk transportation, for example the bulk transportation of solid terephthalic acid so as to store terephthalic acid in the container through a feeding end 3 by applying air pressure from outside, and to take terephthalic acid from a discharging end 4 to the outside. Further, the container has a ventilating end 5 as an air passage.

Up to this time, this ventilating end has been mounted on the container by making a short line slit through a sack body as for a body of a container, inserting a cylindrical film as for a ventilating end into the slit and bonding both of them by heat-sealing.

Now, a process for mounting a ventilating end on a sack body will be explained more in detail with reference to Figs. 10 and 11. Fig. 10 is a perspective view showing the state of a ventilating end 100 mounted on a sack body 102, and Fig. 11 shows its crosssectional view. At first, as shown in Fig. 10, a sack body 102 is prepared by folding both ends of a film 101 and bonding the superposed portion 103 of the folded ends by heatsealing. At this time, by inserting a cylindrical film 104 into the superposed portion 103 P:\OPERUPN2 161301 spe.doc4)8/I0A)1 -2and heat-sealing along the superposed portion 103, production of the sack body and mount of the ventilating end can be attained only in one process. During this time, as shown in Fig. 11, by inserting a fluorocarbon resin sheet 105 inside the cylindrical film 104, bonding both insides of the cylindrical film 104 to each other can be avoided in heat-sealing.

In this production process, a cone summit, or an acute summit is structurally formed in both corners of the heat-sealed portion 106 of the sack body 102 and the cylindrical film 104. Owing to the summits of both comers being cone-shaped, stress due to air pressure in storing or discharging fillings concentrates at these spots and induces the generation of pinholes which start from the summit spot and extend along the heat-sealed portion 106. To this end, measures have hitherto been taken to prevent the lowering of pressure which occurs when pinholes are generated. Typically, pinholes readily develop close to the heat-sealed portion 106 and the container may burst owing to locally applied large stresses. Such measures have included the application of pressure-sensitive tape 107 for reinforcing the container close to the heat-sealed portion 106.

However, these measures require much time taken in operation and induce a rise in cost, and to enhance the adhesive strength of the heat-sealed portion still more is needed.

The present invention seeks to enhance the pressure-resistive strength of a container by improving the ventilating end-mounted design of the container. The present invention also seeks to provide a container in the form of a sack in which the generation of pinholes may be prevented without using a pressure-sensitive tape for reinforcing, and in which bursting of the container may be prevented even when large stress is applied.

In accordance with one aspect of the present invention there is provided a container having a body made of plastic film through which a slit is made and a cylindrical film is inserted therethrough, the body and the cylindrical film being bonded to each other along the periphery of the slit, the bonded portions of the periphery of the slit and the cylindrical film located around both longitudinal ends of the slit having a convex curve projecting toward the inside of the body.

Preferably, both of the bonded portions have a circular or ringed shape for enhancing pressure-resistive strength of the container.

P:\OPERkPN\2 161301 sA.doc4)8/I0/01 -3- In this container, since the corner spot where the sack body and the cylindrical film are bonded has a shape of a convex curve projecting toward the inside of the sack body, the pressure or stress applied to the inside of the sack body may be made deconcentrated without concentrating on the corner of the bonded portion. Accordingly, generation of pinholes can be suppressed, pressure-resistive strength of the container may be enhanced, and consequently, bursting of the container may be prevented.

The present invention is also related to a container in which a reinforcing film is bonded on the aforementioned bonded portion in the same shape as that of the bonded portion. By this reinforcing film, pressure can be deconcentrated as a matter of course the generation of pinholes around a cross point of the two heat seal lines can be suppressed to prevent unwanted breakage of the film along a heat seal line, and thus strength of the bonded portion may be further improved.

In accordance with another aspect of the present invention, there is provided a container having a body approximately in the form of a rectangular parallelepiped, having at one side of the body a feeding end for feeding matter into the body, a discharging end for discharging contents from the body and a ventilating end made of a cylindrical film which is inserted into a slit in the body, the body and the cylindrical film being bonded to each other, the bonded portions of the body and the cylindrical film located around both longitudinal ends of the slit having a convex curve projecting toward the inside of the body. This container aims to have high pressure-resistive strength.

Preferred embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view showing a complete container, and Fig. 2 is its top view.

Fig. 3 is a cross-sectional view for explaining an embodiment of mounting a feeding end and a discharging end.

Fig. 4 is a perspective view of part of a container belonging to one embodiment of the present invention.

Fig. 5 is a cross-sectional view for explaining a process for mounting a ventilating end on a container.

1 11 P:\OPER\JPN\2161301 spc.do-08/l0/0I -4- Figs. 6 and 7 are perspective views regarding part of a container belonging to another embodiment of the present invention.

Fig. 8 is a partially enlarged perspective view around a comer spot shown in Fig. 7.

Fig. 9 is a cross-sectional view regarding part of a container belonging to another embodiment of the present invention.

Fig. 10 is a perspective view for explaining a conventional mounting design for a ventilating end on a container, and Fig. 11 is its cross-sectional view.

The constitution of a container according to the present invention will be described in further detail by way of example with reference to the accompanying drawings.

A container according to the present invention is shown completely in a perspective view of Fig. 1, and its top view is shown in Fig. 2. A container 1 for use in bulk transportation has a sack body 2, which is approximately in the form of a rectangular parallelepiped, and, on one end portion of the longitudinal direction, has a feeding end or feeding passage 3 for use in feeding fillings by pressure from outside, a discharging end or discharging passage 4 for use in discharging fillings out of the sack body, and further, a ventilating end or ventilator 5 required in storing fillings through the feeding end 3 or discharging fillings through the discharging end 4 by air pressure.

Materials of the container should not be limited, but a thermoplastic film or sheet is often used. For example, there can be used plastic film including polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylenevinyl acetate copolymer (EVA), polypropylene, nylon, polyethylene terephthalate (PET) or the like, or otherwise, laminated film of these plastic films with another thermoplastic film.

Appropriate material is selected depending on properties of substances to be filled into the container, filling conditions, and the like. Heat-resistent material is selected for hightemperature feeding and gas barrier material is selected for filling substances easy to be moisturized or oxidized. The film thickness may be 50 to 400 pm, preferably 100 to 300 ,nm. When the film thickness is in this range, film is called "film" or "sheet" in general, for the sake of brevity, only the term "film" has been used hereinafter in this Sspecification.

P:\OPERUPN\2161301 sPd0cA)9lI/(lI1 The above feeding end 3 and discharging end 4 are mounted on the sack body 2 in the same mounting process as suggested in Fig. 3. In this process, approximately circular openings 8 and 9 are made through the positions of the sack body 2 on which either the feeding end 3 or the discharging end 4 respectively is to be mounted. Further, in such a manner as to arrange outside cylindrical films, for providing feeding end 3 and discharging end 4, i.e. cylindrical bodies 6 and 7, the opening 8 of the sack body 2 is covered with the cylindrical body 6 which is then superposed on the periphery of the opening 8 Thereafter, an adhesive material 10 (11) is interposed between the cylindrical body 6 (7) and the opening 8 of the sack body 2, while backing body 12 (13) is put into the cylindrical body 6 Then, the adhesive material 10 (11) is melted by heating and is pressed with heat sealer 14 (15) from outside. Consequently, the cylindrical body 6 is bonded to the sack body 2 along the periphery of the opening 8 thereby the feeding end 3 and discharging end 4 are mounted on the sack body 2 in one piece. Here, when sack body and cylindrical body are made of melt-adhesive materials which make it possible to bond these bodies to each other, the adhesive material 10 (11) may, of course, be eliminated.

A different design from the design for mounting the feeding end 3 and the discharging end 4 on the sack body 2 is applied to a mounting of a ventilating end 5 on the sack body 2, this being one of the improvements provided by an embodiment of the present invention. Fig. 4 is a perspective view of one example of the following mounting design. Namely, through a sack body 2 made of plastic film, which has been gusseted in a diametral direction of the blown film towards a centre thereof, a linear slit 20 is made. Into the slit 20 a cylindrical film 21 for a ventilating end 5 is inserted, and the sack body 2 and the cylindrical film 21 are bonded to each other on the periphery 22 of the slit 20 to form a bonded portion 23. Then, the corner spot 23a, in the bonded portion 23, formed by bonding the periphery 22a positioned at each end of slit 20 along its longitudinal direction and the cylindrical film 21, is formed to have a shape of convex curve projecting toward the inside of the sack body 2, the direction of arrow line A as shown in Fig. 4. In other words, the corner spot 23a should have a shape of convex curve without forming an acute summit toward the inside of the sack body 2. As for the materials of the sack body 2 and the cylindrical film 21, those which are easy to melt and bond to each other are preferable, P:\OPER\JPNM2I6I3OI sp.doM4S/1O/O -6and especially, thermoplastic films of the same material are appropriately used because of having high adhesive strength. Of course, an adhesive layer may be formed between the sack body 2 and the cylindrical film 21 to enhance their adhesive strength.

It is important for both of the corner spots 23a in the bonded portion 23 of the sack body 2 and the cylindrical film 21 to have a shape curved convexly toward the inside of the sack body 2, and by virtue of the convex shape, it is possible to avoid forming a cone summit in the corner spot 23a structurally. Accordingly, even if stress concentration due to air pressure and the like is generated on both of corner spots 23a, stress on these areas will be deconcentrated, and accordingly, sack failure or bursting of the container 1 can be avoided. Usually it is preferable for the corner spot 23a to be generally rounded in the shape of a circle or of an ellipse, or of a polygon having a number of angles not less than that of a hexagon and resembling a circle, an ellipse, or a ring. Otherwise, the shape may be semi-circular or the shape of a tongue as shown in Fig. 4.

Referring to Fig. 5, a process for mounting a ventilating end will now be set forth.

At first, through a plastic sack body 2a a line slit is made, and into the slit 20 a cylindrical film 21 of the same material is inserted. Then, in order to avoid melt adhesion of the cylindrical film 21 between its facing insides, a fluorocarbon resin sheet 30 is inserted into the cylindrical film 21. Further, a fluorocarbon resin sheet 32 is provided outside the cylindrical film 21. While maintaining this state, by heat-sealing in line from outside, sack body 2 and cylindrical film 21 are at first melt-bonded along the periphery 22 of the slit to form a sealed line 26 and unify both of them. Secondly, with a circular heat sealer 31 the periphery 22a and the cylindrical film 21, positioned at both ends of the slit 20 along its longitudinal direction, are melt-bonded to each other while the fluorocarbon resin sheet is sandwiched inside the cylindrical film 21. This gives a container having the corner spot 23a curved convexly toward the inside of the sack body 2.

In this process, the circular heat sealer 31 has a diameter ranging from about 20 to 100 mm, preferably from 40 to 60 mm, and its temperature ranges from 120 to 300 0

C.

preferably from 200 to 250C. This heat sealer may have the shape of a circle, polygon, ring (doughnut) or the like. In the case that the surface of the heat sealer is coated by fluorocarbon resin, adhesion to the film can be avoided, and accordingly, the operation A becomes easier.

-o P:\OPER\JPN\2161301 s p.doc48 10/l I -7- Fig. 6 is a perspective view showing another embodiment of the present invention.

In this embodiment, film 25 for a sack body 2a is folded, a cylindrical film 21 is inserted between the folded film, and heat-sealing is performed near a seam 27, in a linear manner.

This results in melt-bonding the film 25 and the cylindrical film 21 on a seal line 26 as well as melt-bonding the film 25 mutually between its inner surfaces to form a sack body 2a. Accordingly, in this embodiment, the seam 27 substitutes the slit 20 in Fig. 4. Further, in Fig. 6, the bonded portion 23A on the seal line 26, the superposed portion of the sack body 2a and the edge 21a of the cylindrical film 21, corresponds to the corner spot 23a as explained previously in reference to Fig. 4, and on this spot circular heat-sealing is performed to form a convex curve toward the inside of the sack body 2a.

Fig. 7 is a perspective view showing another embodiment of the present invention.

In this embodiment, a film 25, which looks like portions of two sheets of film, is superposed one sheet on the other sheet, a cylindrical film is inserted between the superposed portions of the film, and heat-sealing is performed near the superposed end 28 in a linear manner. This results in melt-bonding the film 25 and the cylindrical film 21 on a seal line 26 as well as the film 25 mutually between its inner faces to form a sack body 2c. Accordingly, in this embodiment, the superposed end 28 area in which the film 25 is not mutually heat-sealed, i.e. the bonded portion of the film 25 and the cylindrical film 21, substitutes the slit 20 in Fig. 4. Further, found in Fig. 7, the bonded portion 23a on the seal line 26, the superposed portion of the sack body 2c and the edge 21 a of the cylindrical film 21, corresponds to the corner spot 23a as explained previously with reference to Fig.

4, and on this spot ringed heat-sealing is performed to form a convex curve toward the inside of the sack body 2c.

Next, as to the corner spot heat-sealed in the ringed shape as shown in Fig. 7, more detailed explanation will now be set forth. Fig. 8 is an enlarged perspective view around the corner spot 23a. In the conventional mounting process of a ventilating end, at an intersection in Fig. 8) of the cylindrical film's edge and a seal line (which corresponds to reference numeral "26" in Fig. 8) produced by heat-sealing a sack body and a cylindrical film inserted into its slit in a linear manner, an acute summit is inevitably formed so that inner stress concentrates on this point, and thereby bursting, of a container has been known to occur in some cases. In contrast to this, in the embodiment of the P\OPERUPNU 16131)1 spe.do xn)8/II)A) -8present invention as shown in Fig. 8, by forming a heat-sealed portion 23a of ringed shape involving the aforementioned intersection, in the corner spot, an unbonded portion 23b of a film 25 and a cylindrical film 21 has a convex curve in outline, stress on the corner spot is deconcentrated, and thereby the container may be prevented from bursting.

Another embodiment of the present invention is shown in Fig. 9 as a crosssectional view. In this embodiment, on a corner spot 23a of a sack body 2 and a cylindrical film 21, reinforcing films 24 of the same material are bonded in the same shape with that of the corner spot 23a in one piece. Namely, during the time of forming the corner spot 23a, the reinforcing films 24 are placed and superposed on the same place and heat-sealing is performed on the reinforcing films 24 to form a convex curve toward the inside of the sack body 2. Thereby, forming of the corner spot 23a and bonding of the reinforcing films 24 can be realized in parallel. In Fig. 6, two sheets of tetragonal reinforcing film 24 bonded on the corner spots 23 in one piece can be seen. In Fig. 7, two sheets of circular reinforcing film 24 sandwiching front and back film 25 are bonded to the corner spot 23a on both sides. In the case that the reinforcing film 24 is bonded on the corner spot 23a in one piece in this way, strength of the corner spot 23a can be increased much more. Other arrangements, equivalent to those in the embodiments as had explained above, may also be realised.

EXAMPLES

In order to check the effect of the aforementioned containers' configurations, in accordance with the above embodiments of the present invention, the following experiments were performed. Now, the present invention will be explained in more detail on the basis of the experimental results. However, it is to be understood that the invention is not intended to be limited to the specific embodiment described.

Example 1 From the composition of low density polyethylene (LDPE, melt flow rate g/10 min.; ASTM D1238) and ethyl-vinyl acetate copolymer (EVA, vinyl acetate content: 5 wt a cylindrical blown or inflation film of 200 num in thickness was formed. By using this film, there was prepared a container shown in Fig. 1 of a rectangular P:\OPERUPlNU161301 spc.do-08/10/MI -9parallelepiped having length of about 5,900 mm, width of about 2,500 mm and height of about 2,400 mm. On this container feeding end 3 and discharging end 4 were mounted, and a ventilating end 5 was mounted in the same manner as that explained with reference to Fig. 4.

Next, all the openings except that of the feeding end 3 were shut. To the feeding end 3 a gas blowing nozzle was connected, and further, a blower was connected to the nozzle. A manometer for measuring pressure in the container was utilized. While the blower was actuated to supply air into the container to gradually increase the pressure in the container, the state of sealing around the bonded portion 23 of the ventilating end 5 was investigated. The result is shown in Table 1.

Example 2 By using the same film of Example 1, the same container of Example 1 was prepared. The same procedure was repeated except that a ventilating end 5a was mounted in the same manner as shown in Fig. 9. The sealing state around the bonded portion 23 of the ventilating end 5a was investigated, and the result is shown in Table 1.

Example 3 By using the same film of Example 1, the same container of Example 1 was prepared. The same procedure was repeated except that a ventilating end5b was mounted in the same manner as shown in Fig. 6. The sealing state around the bonded portion 23 of the ventilating end 5b was investigated, and the result is shown in Table 1.

Comparative Example 1 By using the same film of Example 1, the same container of Example 1 was prepared. Then, a ventilating end 100 was mounted in the same manner as shown in Fig.

but adhesive sheet 107 as shown in Fig. 10 was not used. As to the container thus obtained in the same way as in Example 1, the sealing state around the bonded portion 23 of the ventilating end 5 was investigated while the blower was actuated to supply air into the container, to gradually increase the pressure in the container. The result is shown in Table 1.

m P\OPERJPN2161301 spd-.4)8/l10fi The results shown in Table 1 indicate that the containers of Examples 1 to 3 have improved pressure-resistive strength when compared with the container of Comparative Example 1. Further, the containers of Examples 2 and 3 exhibit better results than that of Comparative Example 1. This suggests that the improving effect of the reinforcing film is considerably high.

Table 1 TEST RESULTS Example 1 The state of a sack body was observed while pressure was gradually increased and then 300 mmAq was maintained for a period of time. As a result, no change was observed. Even though pressure was further increased to 500 mmAq, there were no pinholes generated and no change was observed.

i Example 2 The state of a sack body was observed while pressure was gradually increased and then 300 mmAq was maintained for a period of time. As a result, no change was observed. Even though pressure was further increased to 500 mmAq, there were no pinholes generated and no change was observed. Moreover, there was no symptom of pinholes being generated around the bonded portion, and breakage of the film along a heat seal line was avoided.

Example 3 Approximately the same result of Example 2 was obtained. Namely, no pinholes were generated and no change was observed even though pressure was increased to 300 mmAq, and there was no symptom of pinholes being generated around the bonded portion to prove that breakage of the film along a heat seal line was inhibited even though pressure was increased to 500 mmAq.

P \OPER\JPM2161.101 spe.o4)8/i1f() I 11 Pressure was gradually increased while the state of a sack body was observed. Generation of pinholes at the position structurally Comparative corresponding to a cone summit began at 100 mmAq. When pressure Example 1 was further increased to 200 mmAq, pinholes grew to holes of 50 mm in diameter, and thus the sack body failed as practical value as a sack body was lost.

According to the present invention, the sack body and cylindrical film can be bonded strongly, and this makes it possible to increase pressure-resistive strength of a container. Especially, the corner spot in the bonded portion of the sack body and the cylindrical body does not form an acute summit as can be seen in a conventional container of a sack body but forms a convex curve toward the inside of the sack body. Thus, pressure applied inside the sack body does not concentrate on the corner spot but can be deconcentrated, and accordingly, the generation of pinholes in the bonded portion may be avoided to make it possible to enhance pressure-resistive strength as well as to prevent bursting of the container.

Further, when a reinforcing film is bonded to the corner spot wherein the sack body and the cylindrical film are bonded to each other in the same shape with that of the corner spot in one piece, stress concentration at the corner spot is avoided more surely, the generation of pinholes around the bonded portion may be prevented, and thus breakage of the film along a heat seal line may be avoided. By this application of the reinforcing film, strength of the bonded portion of the sack body and the ventilator may be enhanced much more.

Moreover, in a container according to the present invention, in preparing a sack body from a film, a ventilating end can be mounted in parallel, and it is of reduced importance or needless to use a pressure-sensitive tape for reinforcing, whereas such tape has been used conventionally to enhance strength. Accordingly, the work required in preparing a container may be reduced.

PAOPERUPNU16130J sP.doc4)8/IO/0I 12- It is to be further understood by those skilled in the art that the foregoing description is a preferred embodiment of the disclosed container and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (9)

1. A container having a body made of plastic film through which a slit is made and a cylindrical film is inserted threrethrough, said body and said cylindrical film being bonded to each other along the periphery of said slit, the bonded portions of the periphery of the slit and said cylindrical film located around both longitudinal ends of said slit having a convex curve projecting toward the inside of said body.

2. A container as claimed in claim 1, wherein bonding said body to said cylindrical film is performed by heat-sealing.

3. A container as claimed in claim 1, wherein said slit is formed by cutting said body in a linear manner.

4. A container as claimed in claim 1, wherein said slit is formed through an unsealed portion of a seam in preparing said body by folding a film and sealing the resultant seam. A container as claimed in claim 1, wherein said slit is formed through an unbonded portion in preparing said body by superposing two sheets of film on each other and bonding the superposed portion.

6. A container as claimed in claim 1, wherein each of said bonded portions located around both longitudinal ends of said slit has a shape of a circle.

7. A container as claimed in claim 1, wherein each of said bonded portions located around both longitudinal ends of said slit has a shape of a ring.

8. A container as claimed in claim 1, wherein on each of said bonded portions located around both longitudinal ends of said slit, a reinforcing film is further bonded in the same shape as that of said bonded portion.

9. A container having a body approximately in the form of a rectangular parallelepiped, having at one side of said body a feeding end for feeding matter into said body, a discharging end for discharging contents from said body and a ventilating end made of a cylindrical film which is inserted into a slit in said body, said body and said cylindrical film being bonded to each other, the bonded portions of the body and said cylindrical film located around both longitudinal ends of the slit having a convex curve P:\OPER\JPN2161301 spc.doc48/10/0)

14- projecting toward the inside of said body. A container substantially as hereinbefore described with reference to the accompanying drawings. DATED this 8th day of October, 2001 Mitsui Chemicals, Inc. AND Kyushi-Taiyoukasei., Ltd. By DAVIES COLLISON CAVE Patent Attorneys for the Applicant